Support for global temporaries

doc/ref_transform.rst

loopy/__init__.py

loopy/auto_test.py

loopy/check.py

loopy/codegen/__init__.py

loopy/compiled.py

loopy/kernel/__init__.py

loopy/kernel/creation.py

loopy/kernel/data.py

loopy/preprocess.py

loopy/target/c/__init__.py

loopy/target/pyopencl.py

loopy/transform/buffer.py

loopy/transform/data.py

loopy/transform/precompute.py

loopy/version.py

test/test_loopy.py